The caries is generally referred to as a decayed tooth. It is caused by Streptococcus mutans and other lactic acid bacteria indigenous to the oral cavity which form lactic acid in the bacterial plaque resulting from sucrose etc., in the food. The lactic acid dissolves calcium in the tooth. (This is called decalcification.)
Heretofore, several attempts have been made to prevent caries. They include use of antibiotics, fungicides, an enzyme which dissolves cell walls and medicines having the antibacterial action to prevent the growth of cariogenic bacteria. They also include use of polysaccharide hydrolase to prevent the formation of bacterial plaque. However, those have a disadvantage of disturbing the bacterial flora in the oral cavity and intestine and destroying the natural balance among bacteria. In addition, the use of antibiotics tend to produce side effects. These disadvantages in practical use have not been overcome yet.
In view of these circumstances, as a result of a series of investigations in search for a material having a high antibacterial activity specifically for cariogenic bacteria, it has been found that some of natural vegetable oleoresin have such antibacterial activity.
As a result of further investigations on the vegetable oleoresin (extract by organic solvents) which is effective to inhibit the growth of cariogenic bacteria, it has been found that dihydroguaiaretic acid which is one component therein has the properties to well achieve the object of this invention. The present invention has been attained on the basis of this finding.